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Fencer Vulns
high 8.1

CVE-2026-42533 json

NGINX Map directive and Regex matching vulnerability

published 2026-07-15 3 mo ago modified 2026-11-03 5 d ago also BIT-nginx-2026-42533 , BIT-nginx-gateway-2026-42533 , EUVD-2026-44683

cvss
8.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
6.3%
EPSS 6.3% chance of exploitation in 30 days, percentile 93%
public exploits
0
none known

Summary

A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a string expression references the map's regex capture variables before referencing the map output variable. Alternatively, the same result could be achieved by using a non-cacheable variable in a string expression under certain conditions. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR.

Impact: This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. There is no control plane exposure; this is a data plane issue only.

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Patch / fix

  • bitnami nginx 1.30.4, 1.31.3
  • bitnami nginx-gateway 1.30.4, 1.31.3
  • F5 NGINX Plus 37.0.3.1, R36 P7
  • F5 NGINX Open Source 1.30.4, 1.31.3
  • nginx Debian 12 1.22.1-9+deb12u10
  • nginx Debian 13 1.26.3-3+deb13u8
  • nginx Debian 14 1.30.4-3

debian advisories DEBIAN-CVE-2026-42533

  • nginx Ubuntu 22.04 LTS 1.18.0-6ubuntu14.21
  • nginx Ubuntu 24.04 LTS 1.24.0-2ubuntu7.18
  • nginx Ubuntu 26.04 LTS 1.28.3-2ubuntu1.11
  • nginx Ubuntu Pro 14.04 LTS 1.4.6-1ubuntu3.9+esm9
  • nginx Ubuntu Pro 16.04 LTS 1.10.3-0ubuntu0.16.04.5+esm10
  • nginx Ubuntu Pro 18.04 LTS 1.14.0-0ubuntu1.11+esm5
  • nginx Ubuntu Pro 20.04 LTS 1.18.0-0ubuntu1.7+esm4

ubuntu advisories UBUNTU-CVE-2026-42533

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • nginx RHEL 8 1:1.24.0-3.module+el8.10.0+24848+0300f002.5
  • nginx-mod-mail RHEL 8 1:1.24.0-3.module+el8.10.0+24848+0300f002.5
  • nginx-filesystem RHEL 8 1:1.24.0-3.module+el8.10.0+24848+0300f002.5
  • nginx-mod-stream RHEL 8 1:1.24.0-3.module+el8.10.0+24848+0300f002.5
  • nginx-all-modules RHEL 8 1:1.24.0-3.module+el8.10.0+24848+0300f002.5
  • nginx-mod-http-perl RHEL 8 1:1.24.0-3.module+el8.10.0+24848+0300f002.5
  • nginx-mod-http-xslt-filter RHEL 8 1:1.24.0-3.module+el8.10.0+24848+0300f002.5
  • nginx-mod-http-image-filter RHEL 8 1:1.24.0-3.module+el8.10.0+24848+0300f002.5

red hat advisories RHSA-2026:67315RHSA-2026:67314RHSA-2026:67308RHSA-2026:67283RHSA-2026:66542RHSA-2026:46012

  • nginx SLES 16.0, SLES for SAP applications 16.0 1.27.2-160000.7.1
  • nginx SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Server Applications 15 SP7 1.21.5-150600.10.27.1
  • nginx SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +5 more 1.21.5-150400.3.25.1

suse advisories SUSE-SU-2026:23118-1SUSE-SU-2026:23140-1SUSE-SU-2026:3469-1SUSE-SU-2026:3448-1

  • nginx openSUSE Leap 16.0 1.27.2-160000.7.1
  • nginx openSUSE Tumbleweed 1.31.3-1.1

opensuse advisories openSUSE-SU-2026:21524-1openSUSE-SU-2026:11295-1

  • nginx AlmaLinux 9 2:1.26.3-9.module_el9.8.0+309+b8a3c30d.4
  • nginx-core AlmaLinux 9 2:1.26.3-9.module_el9.8.0+309+b8a3c30d.4
  • nginx-mod-mail AlmaLinux 9 2:1.26.3-9.module_el9.8.0+309+b8a3c30d.4
  • nginx-filesystem AlmaLinux 9 2:1.26.3-9.module_el9.8.0+309+b8a3c30d.4
  • nginx-mod-stream AlmaLinux 9 2:1.26.3-9.module_el9.8.0+309+b8a3c30d.4
  • nginx-all-modules AlmaLinux 9 2:1.26.3-9.module_el9.8.0+309+b8a3c30d.4
  • nginx-mod-http-perl AlmaLinux 9 2:1.26.3-9.module_el9.8.0+309+b8a3c30d.4
  • nginx-mod-http-xslt-filter AlmaLinux 9 2:1.26.3-9.module_el9.8.0+309+b8a3c30d.4

almalinux advisories ALSA-2026:67283ALSA-2026:67308ALSA-2026:67314ALSA-2026:67315ALSA-2026:66542

  • nginx Rocky Linux 10 2:1.26.3-6.el10_2.7
  • nginx Rocky Linux 9 2:1.26.3-9.module+el9.8.0+40222+e48d13b6.1
  • nginx Rocky Linux 9 2:1.26.3-9.module+el9.8.0+40235+8be1317a.2
  • nginx Rocky Linux 9 2:1.26.3-9.module+el9.8.0+40301+37c29bcc.3
  • nginx Rocky Linux 9 2:1.26.3-9.module+el9.8.0+40194+40adfc1b
  • nginx Rocky Linux 9 1:1.24.0-7.module+el9.8.0+40218+76099d32.2.rocky.0.1
  • nginx Rocky Linux 9 1:1.24.0-7.module+el9.8.0+40193+7b2d11e4.1.rocky.0.1
  • nginx Rocky Linux 9 1:1.24.0-7.module+el9.8.0+40300+f1f7491d.4.rocky.0.1

rocky linux advisories RLSA-2026:67314RLSA-2026:67283RLSA-2026:67308RLSA-2026:67315RLSA-2026:66542

  • nginx Alpine 3.21 1.26.3-r2
  • nginx Alpine 3.23, Alpine 3.22 1.28.3-r6
  • nginx Alpine 3.24 1.30.4-r0

alpine advisories ALPINE-CVE-2026-42533

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • nginx Azure Linux 3.0 1.28.3-8

azure linux advisories AZL-92493

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-42533 updated cvss 7.0

nginx: NGINX: Arbitrary code execution via crafted HTTP requests

  • Red Hat Lightspeed proxy 1 insights-proxy/insights-proxy-container-rhel9
    affected: workaround, no fix available
  • Red Hat CodeReady Linux Builder EUS (v.9.6) nginx-debuginfo 1.20.1-22.el9_6.7, nginx-mod-devel 1.20.1-22.el9_6.7, nginx-debugsource 1.20.1-22.el9_6.7, nginx-core-debuginfo 1.20.1-22.el9_6.7, nginx-mod-mail-debuginfo 1.20.1-22.el9_6.7, nginx-mod-stream-debuginfo 1.20.1-22.el9_6.7, +3 more
    fixed: vendor fix RHSA-2026:93467
  • Red Hat Cost Management On-Premise 1 costmanagement/costmanagement-ui-rhel10 1791460851
    fixed: vendor fix RHSA-2026:79357
  • Red Hat Enterprise Linux AppStream (v. 8) nginx 1.24.0-3.module+el8.10.0+24848+0300f002.5, nginx-mod-mail 1.24.0-3.module+el8.10.0+24848+0300f002.5, nginx-filesystem 1.24.0-3.module+el8.10.0+24848+0300f002.5, nginx-mod-stream 1.24.0-3.module+el8.10.0+24848+0300f002.5, nginx-all-modules 1.24.0-3.module+el8.10.0+24848+0300f002.5, nginx-mod-http-perl 1.24.0-3.module+el8.10.0+24848+0300f002.5, +2 more
    fixed: vendor fix RHSA-2026:67315
  • Red Hat Enterprise Linux AppStream (v. 9) nginx 1.20.1-28.el9_8.6, nginx-core 1.20.1-28.el9_8.6, nginx-mod-mail 1.20.1-28.el9_8.6, nginx-filesystem 1.20.1-28.el9_8.6, nginx-mod-stream 1.20.1-28.el9_8.6, nginx-all-modules 1.20.1-28.el9_8.6, +21 more
    fixed: vendor fix RHSA-2026:67308
  • Red Hat Enterprise Linux AppStream (v. 10) nginx 1.26.3-6.el10_2.7, nginx-core 1.26.3-6.el10_2.7, nginx-mod-mail 1.26.3-6.el10_2.7, nginx-filesystem 1.26.3-6.el10_2.7, nginx-mod-stream 1.26.3-6.el10_2.7, nginx-all-modules 1.26.3-6.el10_2.7, +3 more
    fixed: vendor fix RHSA-2026:67314
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) nginx 1.20.1-14.el9_2.7, nginx-core 1.20.1-14.el9_2.7, nginx-mod-mail 1.20.1-14.el9_2.7, nginx-filesystem 1.20.1-14.el9_2.7, nginx-mod-stream 1.20.1-14.el9_2.7, nginx-all-modules 1.20.1-14.el9_2.7, +3 more
    fixed: vendor fix RHSA-2026:93472
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) nginx 1.20.1-16.el9_4.7, nginx-core 1.20.1-16.el9_4.7, nginx-mod-mail 1.20.1-16.el9_4.7, nginx-filesystem 1.20.1-16.el9_4.7, nginx-mod-stream 1.20.1-16.el9_4.7, nginx-all-modules 1.20.1-16.el9_4.7, +3 more
    fixed: vendor fix RHSA-2026:93468
show 5 more
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) nginx 1.20.1-22.el9_6.7, nginx-core 1.20.1-22.el9_6.7, nginx-mod-mail 1.20.1-22.el9_6.7, nginx-filesystem 1.20.1-22.el9_6.7, nginx-mod-stream 1.20.1-22.el9_6.7, nginx-all-modules 1.20.1-22.el9_6.7, +3 more
    fixed: vendor fix RHSA-2026:93467
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) nginx-debuginfo 1.20.1-28.el9_8.6, nginx-mod-devel 1.20.1-28.el9_8.6, nginx-debugsource 1.20.1-28.el9_8.6, nginx-core-debuginfo 1.20.1-28.el9_8.6, nginx-mod-mail-debuginfo 1.20.1-28.el9_8.6, nginx-mod-stream-debuginfo 1.20.1-28.el9_8.6, +3 more
    fixed: vendor fix RHSA-2026:66542
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) nginx-debuginfo 1.26.3-6.el10_2.7, nginx-mod-devel 1.26.3-6.el10_2.7, nginx-debugsource 1.26.3-6.el10_2.7, nginx-core-debuginfo 1.26.3-6.el10_2.7, nginx-mod-mail-debuginfo 1.26.3-6.el10_2.7, nginx-mod-stream-debuginfo 1.26.3-6.el10_2.7, +3 more
    fixed: vendor fix RHSA-2026:67314
  • Red Hat Hardened Images nginx 1.30.4-2.hum1, nginx-core 1.30.4-2.hum1, nginx-mod-mail 1.30.4-2.hum1, nginx-filesystem 1.30.4-2.hum1, nginx-mod-stream 1.30.4-2.hum1, nginx-all-modules 1.30.4-2.hum1, +5 more
    fixed: vendor fix RHSA-2026:46012
  • Red Hat Hardened Images php 8.5.8-2.hum1
    not affected: component not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
3 mo ago

Exploit prediction

6.30% chance of exploitation in the next 30 days, higher than 93% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 4.0 9.2 CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA 4.0 9.2 CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
bitnami nginx
>=0.9.6, <1.30.4
>=1.31.0, <1.31.3
1.30.4
1.31.3
bitnami nginx-gateway
>=0.9.6, <1.30.4
>=1.31.0, <1.31.3
1.30.4
1.31.3

Affected products

  • F5 NGINX Plus
  • F5 NGINX Open Source

Classification

Weakness
  • CWE-122 Heap-based Buffer Overflow
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.